Carotid artery stenosis: performance of advanced vessel analysis software in evaluating CTA

CT Angiography Manual Multiplanar Vessel Diameter Measurement vs. Semiautomated Perpendicular Area Minimal Caliber Computation of Internal Carotid Artery Stenosis

Objective: To determine the diagnostic agreement of CT angiography (CTA) manual multiplanar reformatting (MPR) stenosis diameter measurement and semiautomated perpendicular stenosis area minimal caliber computation of extracranial internal carotid artery (ICA) stenosis.

Methods: We analyzed acute cerebral ischemia CTA at our tertiary stroke center in a 12-month period. Prospective NASCET-type stenosis grading for each ICA was independently performed using (1) MPR to manually determine diameters and (2) perpendicular stenosis area with minimal caliber semiautomated computation to grade luminal constriction. Corresponding to clinically relevant NASCET strata, results were grouped into severity ranges: normal, 1–49%, 50–69%, and 70–99%, and occlusion.

Results: We included 647 ICA pairs from 330 patients (median age of 74 [66–80, IQR]; 38–92 years; 58% men; median NIHSS 4 [1–9, IQR]). MPR diameter and semiautomated caliber measurements resulted in stenosis grades of 0–49% in 143 vs. 93, 50–69% in 29 vs. 27, 70–99% in 6 vs. 14, and occlusion in 34 vs. 34 ICAs (p = 0.003), respectively. We found excellent reliability between repeated manual CTA assessments of one expert reader (ICC = 0.997; 95% CI, 0.993–0.999) and assessments of two expert readers (ICC = 0.972; 95% CI, 0.936–0.988). For the semiautomated vessel analysis software, both intrarater reliability and interrater reliability were similarly strong (ICC = 0.981; 95% CI, 0.952–0.992 and ICC = 0.745; 95% CI, 0.486–0.883, respectively). However, Bland–Altman analysis revealed a mean difference of 1.6% between the methods within disease range with wide 95% limits of agreement (−16.7–19.8%). This interval even increased with exclusively considered vessel pairs of stenosis ≥1% (mean 5.3%; −24.1–34.7%) or symptomatic stenosis ≥50% (mean 0.1%; −25.7–26.0%).

Conclusion: Our findings suggest that MPR-based diameter measurement and the semiautomated perpendicular area minimal caliber computation methods cannot be used interchangeably for the quantification of ICA steno-occlusive disease.

Overcoming calcium blooming and improving the quantification accuracy of percent area luminal stenosis by material decomposition of multi-energy computed tomography datasets

Purpose: Conventional stenosis quantification from single-energy computed tomography (SECT) images relies on segmentation of lumen boundaries, which suffers from partial volume averaging and calcium blooming effects. We present and evaluate a method for quantifying percent area stenosis using multienergy CT (MECT) images. Approach: We utilize material decomposition of MECT images to measure stenosis based on the ratio of iodine mass between vessel locations with and without a stenosis, thereby eliminating the requirement for segmentation of iodinated lumen. The method was first assessed using simulated MECT images created with different spatial resolutions. To experimentally assess this method, four phantoms with different stenosis severity (30% to 51%), vessel diameters (5.5 to 14 mm), and calcification densities (700 to 1100    mgHA / cc ) were fabricated. Conventional SECT images were acquired using a commercial CT system and were analyzed with commercial software. MECT images were acquired using a commercial dual-energy CT (DECT) system and also from a research photon-counting detector CT (PCD-CT) system. Three-material-decomposition was performed on MECT data, and iodine density maps were used to quantify stenosis. Clinical radiation doses were used for all data acquisitions. Results: Computer simulation verified that this method reduced partial volume and blooming effects, resulting in consistent stenosis measurements. Phantom experiments showed accurate and reproducible stenosis measurements from MECT images. For DECT and two-threshold PCD-CT images, the estimation errors were 4.0% to 7.0%, 2.0% to 9.0%, 10.0% to 18.0%, and - 1.0 % to - 5.0 % (ground truth: 51%, 51%, 51%, and 30%). For four-threshold PCD-CT images, the errors were 1.0% to 3.0%, 4.0% to 6.0%, - 1.0 % to 9.0%, and 0.0% to 6.0%. Errors using SECT were much larger, ranging from 4.4% to 46%, and were especially worse in the presence of dense calcifications. Conclusions: The proposed approach was shown to be insensitive to acquisition parameters, demonstrating the potential to improve the accuracy and precision of stenosis measurements in clinical practice.

Systematic review of preoperative carotid duplex ultrasound compared with computed tomography carotid angiography for carotid endarterectomy

INTRODUCTION

We reviewed the literature for preoperative computed tomography carotid angiography and/or carotid duplex to determine their respective sensitivity and specificity in assessing the degree of carotid stenosis. We aimed to identify whether one imaging modality can accurately identify critical stenosis in patients presenting with transient ischaemic attack or symptoms of a cerebrovascular accident requiring carotid endarterectomy.

METHODS

Systematic search of MEDLINE, Embase, Cochrane database of systematic reviews, all Evidence-Based Medicine Reviews (Cochrane Database of Systematic Reviews, ACP Journal club, Database of Abstracts of Reviews of Effects, Cochrane Clinical Answers, Cochrane Controlled Trials Register, Cochrane Methodology Register, Health Technology Assessment and NHS Economic Evaluation Database) for primary studies relating to computed tomography carotid angiography (CTA) and/or carotid duplex ultrasound (CDU). Studies included were published between 1990 and 2018 and focused on practice in the UK, Europe and North America.

RESULTS

The sensitivity and specificity of CTA and CDU are comparable. CDU is safe and readily available in the clinical environment hence its use in the initial preoperative assessment of carotid stenosis. CDU is an adequate imaging modality for determining stenosis greater than 70%; sensitivity and specificity are improved when the criteria for determining greater than 70% stenosis are adjusted. Vascular laboratories opting to use duplex as their sole imaging modality should assess the sensitivity and specificity of their own duplex procedure before altering practice to preoperative single imaging for patients.

CONCLUSIONS

The sensitivity and specificity of CTA (90.6% and 93%, respectively) and CDU (92.3% and 89%, respectively) are comparable. Both are dependent on criteria used in vascular laboratories. CDU sensitivity and specificity was improved to 98.7% and 94.1%, respectively, where peak systolic velocity and end diastolic velocity were assessed. Either modality can be used to determine greater than 70% stenosis, although a secondary imaging modality may be required for cases of greater than 50% stenosis.

Comparison of Measurement and Grading of Carotid Stenosis with Computed Tomography Angiography and Doppler Ultrasound

BACKGROUND

Doppler ultrasound (DUS) and computed tomography angiography (CTA) are the most commonly used imaging modalities for carotid disease. The aim of this study was to test the accuracy and reproducibility of CTA-derived measurements of carotid stenosis and compare them with those obtained by DUS.

METHODS

Images of 100 carotid arteries of patients who underwent carotid DUS at our unit and CTA of the carotids within a 28-day period were identified retrospectively from multidisciplinary team meeting records. CTAs were assessed by 2 investigators, each using a manual and a semi-automated method. With both methods, the degree of stenosis was calculated using the North American Symptomatic Carotid Endarterectomy Trial equation and graded as mild (0-49%), moderate (50-69%), or severe (70-99%). Cohen's kappa and specificity and sensitivity for ≥50% stenosis were calculated.

RESULTS

The interobserver agreement was moderate (κ 0.407, weighted-κ 0.517) for the manual method and good (κ 0.786, weighted-κ 0.842) for the semi-automated method. Using DUS as the gold standard, the semi-automated method had greater sensitivity (75%) and specificity (91%) in detecting clinically significant carotid artery stenosis (≥50%) than the manual one (63% and 86%, respectively). Agreement between DUS and the semi-automated method of CTA reporting was moderate (κ 0.453, 95% confidence interval [CI]: 0.320-0.586, weighted-κ 0.598, 95% CI: 0.486-0.710), whereas DUS and the manual method of CTA reporting had only fair agreement (κ 0.344, 95% CI: 0.209-0.478, weighted-κ 0.446, 95% CI: 0.315-0.577).

CONCLUSIONS

CTA tends to underestimate the degree of stenosis when compared with DUS. The semi-automated method of CTA reporting has greater reproducibility and greater agreement with DUS. These findings have practical implications when CTA is used to measure the degree of carotid stenosis in clinical practice.

The role of multislice computed tomography (MSCT) angiography in the diagnosis and therapy of non-occlusive mesenteric ischemia (NOMI): Could MSCT replace DSA in diagnosis?

Objectives

Evaluation of multislice-CT (MSCT) during diagnosis and therapeutic decision-making in patients with suspected non-occlusive mesenteric ischemia (NOMI).

Methods

Retrospective, institutional review board-approved study of 30 patients (20 men, 10 women, mean age 64.6±14.2 years, range 24–87 years) undergoing biphasic abdominal MSCT followed by digital subtraction angiography (DSA) due to suspected NOMI. MSCT and DSA were qualitatively and quantitatively evaluated independently by two radiologists with respect to the possible diagnosis of NOMI. MSCT analysis included quantitative measurements, qualitative evaluation of contrast enhancement and assessment of secondary findings (bowel wall thickening, hypo-enhancement, intestinal pneumatosis). MSCT diagnosis and secondary findings were compared against DSA diagnosis.

Results

NOMI was diagnosed in a total of n = 28 patients. No differences were found when comparing the R1-rated MSCT diagnosis (p = 0.09) to the “gold standard”, while MSCT diagnosis was slightly inferior with R2 (p = 0.02). With R1, vessel-associated parameters revealed the best correlation, i.e. qualitative vessel width (r = -0.39;p = 0.03) and vessel contrast (r = 0.45;p = 0.01). Moderate correlations were found for quantitative vessel diameters in the middle segments (r = -0.48,p = 0.01), increasing to almost high correlations in the distal (r = -0.66;p<0.00001) superior mesenteric artery (SMA) segments. No significant correlation was apparent from secondary findings.

Conclusions

MSCT is an appropriate non-invasive method for diagnosing NOMI and leads to adequate and immediate therapeutic stratification.